A vehicle may also include one or more cylinders of an engine may be temporarily deactivated to improve vehicle fuel economy. The one or more cylinders may be deactivated by ceasing to supply fuel and spark to the deactivated cylinders. Additionally, air flow into and out of the deactivated cylinders may be prevented, or at least significantly reduced, via closing intake and exhaust valves of the deactivated cylinders. The engine may also be mechanically coupled to a transmission that includes a torque converter. The torque converter allows the engine to rotate without the vehicle having to move and without the engine being completely decoupled from the transmission. Further, an impeller of the torque converter may be locked to a turbine of the torque converter to increase driveline efficiency; however, locking the torque converter may increase driveline noise vibration and harshness (NVH). The driveline may be at a higher efficiency when cylinders are deactivated and when the torque converter is locked, but driveline vibrations may be greater than desired during such conditions. Therefore, it may be desirable to provide a method that provides higher levels of driveline efficiency without vehicle occupants having to tolerate undesirable levels of vehicle vibration and noise.
The inventors herein have recognized the above-mentioned limitations and have developed an engine control method, comprising: increasing an actual total number of operating cylinders from a first actual total number of operating cylinders to a second actual total number of operating cylinders via a controller in response to slip of a torque converter exceeding a threshold, the threshold a function of a fuel benefit and a fuel penalty.
By increasing the actual total number of operating cylinders in response to slip of a torque converter exceeding a threshold, the threshold a function of a fuel benefit and a fuel penalty, it may be possible to provide the technical result of operating an engine in a cylinder deactivation mode and controlling torque converter slip such that driveline efficiency is high and vehicle passengers are not disturbed by driveline noise. For example, an eight cylinder engine may change from a four cylinder operating mode to a six or eight cylinder operating mode when torque converter slip exceeds a threshold that indicates that increasing an actual total number of operating cylinders may be more effective to control NVH and operate the driveline efficiently.
The present description may provide several advantages. In particular, the approach may provide improved vehicle fuel economy with reduced NVH. In addition, the approach may reduce the possibility of disturbing occupants of a vehicle while cylinders are deactivated. Further, the approach provides a useful way of resolving whether it is more beneficial to increase slip of a torque converter to improve driveline NVH or activate additional cylinders to improve NVH.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.